A man who had his bedding on the top of an elevator car at the Montgomery Station in San Francisco was crushed when a patron tried to take the car to the top level, BART police said Monday.

The subway patron was riding the elevator at Sansome and Sutter streets from the Muni Metro platform to the concourse level at 9:26 p.m. Sunday when he heard a crunching sound and a scream, said BART police Lt. Michael Hayes.

The elevator became stuck, and the patron called police. When rescuers arrived, they found the man in the elevator shaft dead and surrounded by bedding.

"We don't know why he sought refuge in our elevator shaft," said Luna Salaver, a BART spokeswoman. "We don't know how long he was in there, and we don't know how he accessed our shaft."

No one at BART has ever heard of a homeless person sleeping on top of an elevator car, Salaver said. Crews were examining all elevator shafts in downtown San Francisco stations Monday to make sure they were empty, she said.

Regulators with the Cal/OSHA Elevator Ride and Tramway Unit will also investigate the incident, Salaver said. BART hopes to reopen the elevator by March 20.